The burgeoning North Rim population threatens vegetation, water and cultural sites.

BACKSTORYIn 2003, drought drove a herd of bison into Grand Canyon National Park from the adjacent Kaibab National Forest, where they had been imported in the 1930s to crossbreed with cattle. State-permitted hunts kept the herd under 200, but as its usual range dried up, the huge animals sought greener pastures on the North Rim, wallowing in riparian areas and damaging archaeological sites. Park managers, worried about impacts to land and visitors, sought to remove the unwanted herd (“Bison arrive in Grand Canyon uninvited”, HCN, 4/28/03).

FOLLOWUP In September, the National Park Service announced that over the next three to five years, it would cull the North Rim herd, now about 600 animals, to fewer than 200. The agency plans to round up some bison and ship them to tribes and cooperating agencies. Skilled volunteer shooters, chosen by lottery, will hunt the rest. Without culling, biologists say, herd numbers could hit 1,500 within 10 years.